1. Field of the Invention
The present invention relates to a current sensor for measuring currents to be measured flowing through various kinds of devices, using a magnetoelectric conversion element, and in particular, relates to a current sensor suitable for a case where the frequencies of currents to be measured flowing through various kinds of devices each of which is equipped with an inverter or the like vary.
2. Description of the Related Art
In recent years, in order to control or monitor various kinds of devices, usually current sensors attached to the various kinds of devices and configured to measure currents to be measured flowing through the various kinds of devices have been used. As a current sensor of this kind, a method has been well known that utilizes a magnetoelectric conversion element (magnetic detecting element) such as a magnetoresistance effect element or a Hall element, used for sensing a magnetic field generated from a current to be measured flowing through a current path.
Among the above-mentioned current sensors, such a current measurement apparatus (current sensor) 900 as proposed in Japanese Unexamined Patent Application Publication No. 2005-70037 has been generally known that utilizes a flat-shaped conductor to be measured (current path) and a magnetic sensor arranged on an insulating substrate. FIG. 27 is a diagram explaining the current measurement apparatus 900 disclosed in Japanese Unexamined Patent Application Publication No. 2005-70037 and is a cross-sectional view illustrating a positional relationship between a magnetic sensor 910 and a conductor to be measured 901. As illustrated in FIG. 27, the current measurement apparatus 900 includes the conductor to be measured 901 formed in a printed substrate 911 and the magnetic sensor 910 (equipped with a magnetic detecting element) mounted in a printed substrate 912 and detects, using the magnetic sensor 910, a magnetic field 920 generated in the width direction of the conductor to be measured 901 when a current to be measured flows through the conductor to be measured 901.
By the way, if the frequency of the current to be measured flowing through such a flat-shaped conductor to be measured 901 increases, the current to be measured is concentrated into end portions of the conductor to be measured 901 by a skin effect, a current density becomes small in the middle of the conductor to be measured 901, and the current density becomes large in the vicinities of ends of the conductor to be measured 901. Therefore, in a case where the magnetic sensor 910 is disposed in the middle of the conductor to be measured 901 (disposed in an end portion, in FIG. 27), there has been a problem that the magnetic field 920 in the vicinity of the middle, sensed by the magnetic sensor 910, is reduced and the current sensitivity of the current measurement apparatus 900 is reduced.
Therefore, in the current measurement apparatus 900 of the related art, as illustrated in FIG. 27, the magnetic sensor 910 is provided at a position located a predetermined distance away from the central position CL of the conductor to be measured 901 in the width direction thereof. From this, it is assumed that it is possible to provide the current measurement apparatus 900 in which the reduction of the measurement sensitivity is suppressed even in a case of a current to be measured whose frequency is high.
However, in the related art, the magnetic sensor 910 is disposed in the vicinity of an end of the conductor to be measured 901 in accordance with the frequency of the current to be measured, scheduled to be measured. Therefore, there has been a problem that, in a case of being applied to another device utilizing a current to be measured whose frequency is different or in a case where a frequency changes based on a state even in a case of the same device, the sensitivity of a current measured in the current measurement apparatus 900 widely varies and it is difficult to obtain correct measurement accuracy. In addition, as the case where the frequency of the current to be measured changes based on a state, a case may be cited in which, in, for example, an electric vehicle or a hybrid vehicle, the frequency of the current to be measured changes based on states such as at the time of idling, at the time of acceleration, and at the time of regenerative brake.
The present invention solves the above-mentioned problem and provides a current sensor capable of accurately measuring a current to be measured even if the frequency of the current to be measured changes.